C++ STL Alternatives to Non-STL Code

Below is a collection of examples of common code patterns that could otherwise be written simpler, cleaner, and more correct when the STL or boost is used.

Call a Function with Each Value in a Sequence

for (size_t x = 0; x < v.size(); x++)
{
    func(v[x]);
}

std::for_each(v.begin(), v.end(), func);

Get the Sum of a Sequence

long long z = 0;
for (size_t x = 0; x < v.size(); x++)
{
    z += v[x];
}

long long z = std::accumulate(v.begin(), v.end(), 0LL);

Be careful with std::accumulate.

Get the Product of a Sequence

long long z = 1;
for (size_t x = 0; x < v.size(); x++)
{
    z *= v[x];
}

long long z = std::accumulate(v.begin(), v.end(), 1, std::multiplies<long long>());

Write the Values of a Sequence to a Stream

std::ostringstream ss;
for(size_t x = 0; x < v.size(); x++)
{
    ss << v[x] << "\n";
}

std::ostringstream ss;
std::copy(v.begin(), v.end(), std::ostream_iterator<int>(ss,"\n"));

Read the Contents of a File Into a String

std::string data;
std::ifstream in(filename.c_str());
do
{
   char ch = in.get();
   if (in)
   {
      data.push_back(ch);
   }
} while(in);

std::string data;
std::ifstream in(filename.c_str());
std::copy(std::istreambuf_iterator<char>(in), 
          std::istreambuf_iterator<char>(), 
          std::back_inserter(data));

Reverse a Sequence

for (size_t i = 0; i < v.size()/2; i++)
{ 
   std::swap(v[v.size()-i-1],v[i]);
}

std::reverse(v.begin(),v.end());

Fill a Sequence With Generated Values

int RandomNumber () { return (std::rand()%100); }
 
std::srand(unsigned(std::time(0)));
std::vector<int> v;
for (size_t x = 0; x < 10;x++)
{
   v.push_back(RandomNumber());
}

std::vector<int> v(10);
std::generate(v.begin(), v.end(), RandomNumber);